from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from sqlalchemy.ext.asyncio import AsyncSession
from database import async_session
from jose import JWTError, jwt
from datetime import datetime, timedelta, timezone
from typing import Optional
import crud
from schemas import UserOut

# JWT Configuration
SECRET_KEY = "your-secret-key"  # Change this to a strong secret in production
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="login")

async def get_db():
    """Provide a database session"""
    async with async_session() as session:
        yield session

def create_access_token(data: dict, expires_delta: Optional[timedelta] = None):
    """Create a JWT access token"""
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt

async def get_current_user(token: str = Depends(oauth2_scheme), db: AsyncSession = Depends(get_db)):
    """Validate JWT token and return current user"""
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
    user = await crud.get_user_by_username(db, username=username)
    if user is None:
        raise credentials_exception
    return user